Enabling new biomedical and bioinspired mechatronic systems with electroactive smart elastomers Federico Carpi 1

EAP are materials capable of changing dimensions and/or shape in response to suitable electrical stimuli (Stanford Research Institute) Example: dielectric elastomer actuator Electromechanically Active Polymers (EAP) 2

3

thickness compression surface expansion Electrostatic pressure: p = ε 0 ε r E 2 Thin insulating elastomeric film sandwiched between two compliant electrodes:  4 Dielectric elastomer actuators

Thin film of insulating elastomer sandwiched between two compliant electrodes, so as to obtain a deformable capacitor. Electrical charging results in an electrostatic compression of the elastomer. Stanford Research Institute Pelrine, Kornbluh, Pei, et al. Dielectric elastomer actuators (our group) 5

How to use the DE actuation principle? Possibilities for new devices and applications limited only by imagination! The greatest value of this technology lies in the fact that it is extremely ‘poor’ (‘poor’ materials and extremely simple mechanism) 6

(Stanford Research Institute) (Our group) Dielectric elastomer actuators

Properties: 1)Inherently capable of changing dimensions and/or shape in response to suitable electrical stimuli, so as to transduce electrical energy into mechanical work. In that, they show attractive propeties as engineering materials for actuation: -efficient energy output, -high strains, -high mechanical compliance, -shock resistance, -low mass density, -no acoustic noise, -ease of processing, -high scalability -low cost. 2)Can also operate in reverse mode, transducing mechanical energy into the electrical form. Therefore, they can also be used as mechano-electrical sensors, as well as energy harvesters to generate electricity. 3) Capable of stiffness control. 4) Can combine actuation, sensing and stiffness control, not only in the same material, but actually in the viscoelastic matter they are made of, showing functional analogy with natural muscles artificial muscles Dielectric elastomer actuators

… artificial skeletal muscles … Not today Main challenges: - need for improved actuating configurations - need for higher energy density (natural muscle performance can be exceeded, but only in exceptional conditions) - need for lower driving voltages - mechanical interfaces with the body A dream in the biomedical field…

Compressive stress (Maxwell stress): ε 0 =8.854 pF/m: dielectric permittivity of vacuum E= applied electric field ε= relative dielectric permittivity of the elastomer Need for new high-permittivity elastomers: composites blends new synthetic polymers 1) FIRST APPROACH: increasing the material dielectric constant 2) SECOND APPROACH: reducing the film thickness V= applied voltage d= thickness Reducing the driving voltages 10

1) Full-page refreshable and portable Braille displays for the blind people 2) Wearable tactile display for virtual interactions with soft bodies 3) Haptic or visual displays of tissue compliance or organ motility 4) Artificial ciliary muscles for electrically tuneable optical lenses for artificial vision systems 5) Artificial muscles for electrically stretchable membrane bioreactors Contributions from our group: Biomedical & bioinspired applications

1) Full-page refreshable and portable Braille displays for the blind people 2) Wearable tactile display for virtual interactions with soft bodies 3) Haptic or visual displays of tissue compliance or organ motility 4) Artificial ciliary muscles for electrically tuneable optical lenses for artificial vision systems 5) Artificial muscles for electrically stretchable membrane bioreactors Contributions from our group: Biomedical & bioinspired applications

Artistic view of a possible Braille tablet/e-Book This is science fiction today! Full-page refreshable and portable Braille displays for the blind people

STATE OF THE ART Full-page refreshable and portable Braille displays for the blind people

STATE OF THE ART piezoelectric cantilever actuators Assembling two lines of Braille cells requires putting two series of actuators nose-to-nose, with their cantilevers pointing away from the cells, laterally 10 cm 3 cm > 20 cm Full-page refreshable and portable Braille displays for the blind people

STATE OF THE ART piezoelectric cantilever actuators cm Thickness 3-4 cm Assembling two lines of Braille cells requires putting two series of actuators nose-to-nose, with their cantilevers pointing away from the cells, laterally Full-page refreshable and portable Braille displays for the blind people

F. Carpi, G. Frediani, D. De Rossi, “Hydrostatically coupled dielectric elastomer actuators”, IEEE/ASME Transactions On Mechatronics, vol. 15(2), pp , OUR APPROACH: Bubble-like ‘hydrostatically coupled’ DE actuators Full-page refreshable and portable Braille displays for the blind people

Dielectric elastomer film: silicone (Elastosil RT625, Wacker) processed as a thin film by Danfoss PolyPower Film thickness: about 66  m (two films stacked together) Transmission medium: vegetable (corn) oil Max voltage: 2.25 kV Prototypes Full-page refreshable and portable Braille displays for the blind people

- Simple and compact structure; - Ease of fabrication (  low cost) - Electrical safety: i) passive end-effector (no need for insulating coatings) ii) dielectric fluid (as a further protection); - Self-compensation against local deformations caused by the finger: the shape and the thickness uniformity of the active membrane are preserved Attractive features for tactile displays: Full-page refreshable and portable Braille displays for the blind people

Refreshable Braille cell based on Hydrostatically Coupled DE actuators: External electrodes Internal electrodes TOP PASSIVE MEMBRANE BOTTOM ACTIVE MEMBRANE Plastic frame Braille dot Full-page refreshable and portable Braille displays for the blind people

Thickness 1-2 mm 4 cm cm Thickness 3-4 cm Potential advantages over the state of the art: 1)Compact size 2)Suitability for ‘full-page’ displays 3) Light weight 4) Shock tolerance 5) Low cost state of the art Refreshable Braille cell based on Hydrostatically Coupled DE actuators: Full-page refreshable and portable Braille displays for the blind people

Prototype samples Elastomer film: 3M VHB 4905 acrylic polymer. Bi-axial pre-stretching: 4 times. Pre-stretched thickness: about 30 µm. Electrode material: carbon conductive grease. Transmission medium: silicone grease Refreshable Braille cell based on Hydrostatically Coupled DE actuators: Full-page refreshable and portable Braille displays for the blind people

Early prototype with Braille dots and spacing oversized (up-scaled) with respect to standards. Refreshable Braille cell based on Hydrostatically Coupled DE actuators: Full-page refreshable and portable Braille displays for the blind people

Braille dot with standard size (diameter = 1.4 mm; height = 0.7 mm) Refreshable Braille cell based on Hydrostatically Coupled DE actuators: Full-page refreshable and portable Braille displays for the blind people

1) Full-page refreshable and portable Braille displays for the blind people 2) Wearable tactile display for virtual interactions with soft bodies 3) Haptic or visual displays of tissue compliance or organ motility 4) Artificial ciliary muscles for electrically tuneable optical lenses for artificial vision systems 5) Artificial muscles for electrically stretchable membrane bioreactors Contributions from our group: Biomedical & bioinspired applications

Wearable tactile display for virtual interactions with soft bodies G. Frediani, D. Mazzei, D. De Rossi, F. Carpi, “Wearable wireless tactile display for virtual interactions with soft bodies”, Frontiers in Bioengineering and Biotechnology, Vol. 2, 2014.

Wearable tactile display for virtual interactions with soft bodies G. Frediani, D. Mazzei, D. De Rossi, F. Carpi, “Wearable wireless tactile display for virtual interactions with soft bodies”, Frontiers in Bioengineering and Biotechnology, Vol. 2, 2014.

Wearable tactile display for virtual interactions with soft bodies G. Frediani, D. Mazzei, D. De Rossi, F. Carpi, “Wearable wireless tactile display for virtual interactions with soft bodies”, Frontiers in Bioengineering and Biotechnology, Vol. 2, Video

1) Full-page refreshable and portable Braille displays for the blind people 2) Wearable tactile display for virtual interactions with soft bodies 3) Haptic or visual displays of tissue compliance or organ motility 4) Artificial ciliary muscles for electrically tuneable optical lenses for artificial vision systems 5) Artificial muscles for electrically stretchable membrane bioreactors Contributions from our group: Biomedical & bioinspired applications

(dots: liver) (dots: stomach) Force feedback in minimally invasive surgery F. Carpi et al. IEEE Transactions on Biomedical Engineering, Vol. 56(9), pp , Controlling the stiffness to simulate different tissues Haptic or visual displays of tissue compliance or organ motility

31 (Control via EMG) (Control via respiration) (Control via ECG) Haptic or visual displays of tissue compliance or organ motility Medical training

1) Full-page refreshable and portable Braille displays for the blind people 2) Wearable tactile display for virtual interactions with soft bodies 3) Haptic or visual displays of tissue compliance or organ motility 4) Artificial ciliary muscles for electrically tuneable optical lenses for artificial vision systems 5) Artificial muscles for electrically stretchable membrane bioreactors Contributions from our group: Biomedical & bioinspired applications

Artificial vision (computer vision) systems in the biomedical field: - Social robots (e.g. robot therapy) - Medical diagnostics (e.g. video endoscopes and other optical instrumentation, lab-on-a-chip units, etc.) - etc. Conventional optical focalization : focal length tuning achieved by displacing one or more constant-focus lenses.  moving parts  miniaturization is complex and expensive,  bulky structures Need for tunable-focus lenses with no moving parts Electrically tuneable optical lenses for artificial vision systems

F. Carpi et al., “Bioinspired tunable lens with muscle-like electroactive elastomers”, Advanced Functional Materials, Artificial ciliary muscles for electrically tuneable optical lenses

F. Carpi et al., “Bioinspired tunable lens with muscle-like electroactive elastomers”, Advanced Functional Materials, Artificial ciliary muscles for electrically tuneable optical lenses

F. Carpi et al., “Bioinspired tunable lens with muscle-like electroactive elastomers”, Advanced Functional Materials, Bioinspired lens Human crystalline Artificial ciliary muscles for electrically tuneable optical lenses

F. Carpi et al., “Bioinspired tunable lens with muscle-like electroactive elastomers”, Advanced Functional Materials, Artificial ciliary muscles for electrically tuneable optical lenses

F. Carpi et al., “Bioinspired tunable lens with muscle-like electroactive elastomers”, Advanced Functional Materials, cm 10 cm Artificial ciliary muscles for electrically tuneable optical lenses

L. Maffli, S. Rosset, M. Ghilardi, F. Carpi, H. Shea, "Ultrafast all-polymer electrically tuneable silicone lenses", Advanced Functional Materials, in press. Artificial ciliary muscles for electrically tuneable optical lenses WORLD’S FASTEST AND THINNEST tuneable lens: settling time < 175 μs for a 20% change in focal length Low-loss silicone Be-spoke manufacturing Cooperation with EPFL (Prof. Herbert Shea’s group)

L. Maffli, S. Rosset, M. Ghilardi, F. Carpi, H. Shea, "Ultrafast all-polymer electrically tuneable silicone lenses", Advanced Functional Materials, in press. Artificial ciliary muscles for electrically tuneable optical lenses WORLD’S FASTEST AND THINNEST tuneable lens:

1) Full-page refreshable and portable Braille displays for the blind people 2) Wearable tactile display for virtual interactions with soft bodies 3) Haptic or visual displays of tissue compliance or organ motility 4) Artificial ciliary muscles for electrically tuneable optical lenses for artificial vision systems 5) Artificial muscles for electrically stretchable membrane bioreactors Contributions from our group: Biomedical & bioinspired applications

SLIDES ON THIS PART HAVE BEEN REMOVED FROM THIS ONLINE VERSION OF THIS PRESENTATION, AS RESULTS ARE NOT PUBLISHED YET 43 Artificial muscles for electrically stretchable membrane bioreactors

Inustrialization of the dielectric elastomer technology is living its infancy nowadays… Dielectric elastomer actuators

Main EAP developers Today the EAP field is just starting to undergo transition from academia into commercialization (developers of transducers based on piezoelectric and electrostrictive polymers not included) EAP industrialization

European Scientific Network for Artificial Muscles (ESNAM) 68 Member organizations from 26 European countries:

Relevant website: “EuroEAP”

‘EAPosters’ ‘EAPodiums’ ‘EAProducts’ Relevant event: “EuroEAP conference” Annual International conference on Electromechanically Active Polymer (EAP) transducers & artificial muscles

Relevant event: “EuroEAP conference” EuroEAP 2015 Tallin, Estonia 9-10 June EuroEAP Pisa, Italy EuroEAP Potsdam, Germany EuroEAP Zurich, Switzerland EuroEAP Linköping, Sweden